Mechanical timepieces with complex structure and more elaborated functions, in particular also in terms of driving and regulation of the movement, are popular and are becoming increasingly widespread. Tourbillons are to be regarded in this context as well since being used to make the effect of the force of gravity on the accuracy of the movement of the timepiece independent of the orientation of the timepiece in space by arranging the regulating organ and the escapement of the timepiece on a continuously rotating frame, which is also referred to as a tourbillon. Although this effect needs to be relativized in the case of wristwatches due to the continuous arm movement occurring as the timepiece is worn under normal circumstances, it is indispensable to synchronize the time of mechanical timepieces from time to time with a time indication that is as exact as possible, for example with the aid of a commercially available radio clock controlled by an atomic clock.
However, it is difficult in the case of timepieces having a tourbillon to ensure a precise manual adjustment of the time since the tourbillon, respectively the balance mounted therein has to be stopped. In fact, in such devices all components of the escapement and the balance with the associated balance spring are mounted within the mobile carriage of the tourbillon, which is also referred to as the tourbillon cage. The latter usually consists of what are known as the lower part and upper part, which are connected by a number of columns secured to the outer edge of the cage. The balance located in the rotating tourbillon cage and oscillating therein thus cannot be stopped easily due to the columns of the mobile carriage which are forming an obstacle and are continuously rotating.
On the one hand, this has led to the use in some timepieces of movements having a tourbillon, however entirely without associated stop device for the balance, which in the corresponding timepieces results in the serious disadvantage of a synchronous adjustment of the time that is not accurate to the second. For the sake of completeness, it is noted here that a tourbillon cage or mobile carriage can act as a second hand if the construction has been designed such that the cage rotates once per minute about its own axis. This is, amongst others, the reason why most timepieces with a tourbillon cage visible from the dial side do not require a second hand, wherein however there is the above-mentioned disadvantage that it is not possible, due to the lack of a second hand and therefore the lack of a conventional second stop device, to adjust such tourbillon timepieces in a manner accurate to the second. In addition, it shall also be noted here that a conventional second stop device for second hands known to the person skilled in the art, as described for example in document CH 220 530 (Thommens Uhrenfabriken AG), anyway cannot act as a stop device accurate to the second in timepieces designed in this way with a tourbillon because, as mentioned above, the balance, due to the construction, is arranged almost unattainably within the continuously rotating mobile carriage of the tourbillon.
On the other hand, in view of the above-mentioned disadvantage which considerably compromises the advantage of the increased accuracy of a movement with tourbillon, there have been proposed over time various mechanisms allowing the movement to be stopped in a tourbillon and therefore, in principle, allowing the time to be adjusted in a manner accurate to the second. Examples for this include for example the tourbillon devices described in documents WO2003/048871 (Lange Uhren GmbH), EP 1 617 305 (Montres Breguet SA), CH 699 029 (Fabrique d'horlogerie Minerva SA), and CN101846962 (Tianjin Sea Gull Watch Group Co Ltd).
Without being able to go into extensive detail with regard to these devices, it is noted that the mechanism proposed in document WO2003/048871 (Lange Uhren GmbH) concerns a timepiece having a tourbillon, wherein the timepiece has a stop device which is based substantially on a V- or U-shaped double-arm spring that can be pivoted from a normal position radially outside the orbital path of movement of the columns of the tourbillon cage into a blocking position, in which the free ends of said spring rest against the balance and suppress the movement thereof. This approach based on a double-arm spring requires a lot of space for the pivoting motion of the double-arm spring and is relatively complicated both in terms of the structure and of the operating principle.
The tourbillon according to document EP 1 617 305 (Montres Breguet SA) has a plurality of blocking elements along the tourbillon cage which are controlled from outside the cage and which can stop the balance mounted in the tourbillon cage. However, the tourbillon per se must be changed as a result of this approach by the addition of further components, without any gain in terms of the simplicity and reliability of the mechanism.
Document CH 699 029 (Fabrique d'horlogerie Minerva SA) proposes a tourbillon that no longer requires any columns and therefore no longer has a tourbillon cage in the conventional sense due to the fact that an end of the axis of the balance of said tourbillon is mounted in a stationary bridge of the timepiece. In this device the balance, similarly to a balance in a movement without tourbillon, can therefore be stopped by means of a laterally mounted stop lever. However, this device is suitable only for movements or timepieces in which the conventional tourbillon cage with the characterizing columns thereof can be omitted or should be omitted.
Lastly, document CN 101 846 962 (Tianjin Sea Gull Watch Group Co Ltd) discloses a tourbillon with which the balance mounted in the cage can be stopped by stop pliers acting on the axis of the balance. Due to the short lever arm, however, the stop force exerted on the axis by the stop pliers has to be selected to be very high, wherein it may additionally take a comparatively long time to stop the balance.